Wireless products such as base stations, access points and wireless devices need to be thoroughly tested during the development phase before being deployed in commercial networks. Ideally these wireless products should be tested in the same way as they will be used. For example, wireless devices will be used to transmit and receive signals over the air, so the ideal test environment is over the air.
Driving test is commonly used for over the air testing. To perform a driving test, a vehicle, or multiple vehicles, are required to carry the wireless device(s). In order to test base station capacity in an over-the-air network, hundreds if not thousands of wireless devices are needed, not to mention that each and every wireless device requires an operator. Thus, the cost of conducting over-the-air capacity testing is prohibitive.
An alternative solution to over the air testing is to perform testing in a laboratory environment. In laboratory testing, a base station and wireless device are connected using Radio Frequency cables. Between the base station and wireless device, equipment such as a channel emulator can be added to emulate wireless communication channels. Using the channel emulator, wireless devices can be tested extensively. Some existing channel emulators include a feature known as a Geometry Based Channel Model (GBCM). The GBCM feature can simulate wireless device locations in a cabled lab environment and is used to test advanced features of the wireless device such as beamforming, Advanced Antenna System (AAS) and massive Multiple Input Multiple Output (MIMO), etc.
Existing GBCM features do suffer from various limitations in that a wireless device is either placed at a fixed location or is moving along a predefined drive route(s) due to the channel emulation. In either case, the system under test is evaluated at predetermined locations. Performance measured at those pre-determined locations is not a true representation of the system wide performance of the system, and it is the system wide (or network wide) performances that are closely monitored by the wireless providers. Hence, the use of predetermined locations for channel emulation for wireless device testing is lacking.
To further explain the shortcomings of the existing channel emulation schemes, beamforming will be discussed within the context of the channel emulator. Performance of the beamforming algorithm is dependent on a geographical location of the wireless device. At different azimuths, the benefit of beamforming algorithm (relative to non-beamforming) can vary due to non-uniform antenna beam patterns. To characterize network wide performance, measurement samples collected from a large quantity of uniformly distributed random locations would be needed.
Further, channel emulators are not the only piece of equipment that can emulate wireless channels. Existing wireless device simulators that are used to simulate hundreds or thousands of wireless devices also have the capability to emulate time-varying RF channels. However, the channel emulation capability of these wireless device simulators is limited. For instance, the wireless device simulators do not have the ability to emulate the GBCM feature, discussed above. As such, known wireless device simulators have limited use in testing beamforming and AAS.
In summary, due to various limitations associated with existing channel emulators and wireless device simulators, existing system are not able to provide accurate results to predict network wide performance.